This topic has just come up again on our PN forum here. So I did some new searching to update information on this topic:

So here are the links. The first ones deal with high serum levels when no supplements are taken. This topic is all over the web so it has to be affecting many people.

The Cause of Vitamin B6 Toxicity is Not What You Think

[How much vitamin B6 is toxic?]. - PubMed - NCBI

Elevated B6 levels and peripheral neuropathies. - PubMed - NCBI

And this last paper which is a PDF, explains the chemical reactions and binding to pyridoxal kinase, which is the enzyme which activates pyridoxine ( to pyridoxal 5 phosphate). At the end of the paper is a new list of drugs found to impair this conversion (impairing pyridoxal kinase's actions), and has added new drugs to the list which may affect many people.
It has a heading numbered 5.4

http://scholarscompass.vcu.edu/cgi/v...07&context=etd

Also if one searches, "drugs that affect pyridoxal kinase" one can find papers suggesting antimalarials mentioned. These are quinoline derivatives, and I suspect fluoroquinolines might be appearing soon in this research as well.

Back when pyridoxal kinase was first being studied, over a decade ago, I only found theophylline listed as a inhibitor of this enzyme.
It appears then, with more time, other drugs will be added as well to this list.